17 Aug
2019
17 Aug
'19
9:14 a.m.
I've never heard of people using DB25 for 20mA, at
least historically,
contemporaneous with its widespread actual use. E.g. DEC
universally used
'flat' 8-pin Mate-n-Lok connectors for 20mA serial connections.
Thanks for the comments... I asked mostly because the ADM-3A has both RS-232
and current loop interfaces built-in (on the same female DB-25), selected by
one of the
DIP switches.
I just hate having to make a custom cable for every terminal and computer I
own or work with ;)
-Charles
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17 Aug
17 Aug
10:12 a.m.
Thanks for the comments... I asked mostly because the ADM-3A has both
RS-232
and current loop interfaces built-in (on the same female DB-25), selected
by
one of the
DIP switches.
I just hate having to make a custom cable for every terminal and computer I
own or work <snip
I have some specific pinouts for current loop on my site... for dec pdp
11/05, swtpc 6800, altair 680, and rs232 to current loop conversion.
Vintagecomputer.net
Bill
11:50 a.m.
In my prior life as an EE, I had to do it many times (early 80's)... I may
be nostalgic, but not THAT nostalgic :)
-----Original Message-----
From: Chris Hanson
Sent: Saturday, August 17, 2019 1:37 PM
To: Charles ; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Pinout for current loop interface
On Aug 17, 2019, at 9:14 AM, Charles via cctalk <cctalk at classiccmp.org>
wrote:
I just hate having to make a custom cable for every
terminal and computer
I
own or work with ;)
Ah, but isn?t doing what so many before you have had to part of the charm?
:)
-- Chris
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noon
You haven't lived until you have played with live long-line teletype
current loop circuits. In my first job as an FE on a Univac that was a
store and forward message switcher, we had racks of mercury relays
feeding the teletype lines, which ran at 130VDC to give the current
needed to get to the next hop! Working in that rack could result in some
very sudden surpsies!
cheers,
Nigel
On 17/08/2019 14:50, Charles via cctalk wrote:
In my prior life as an EE, I had to do it many times
(early 80's)... I
may be nostalgic, but not THAT nostalgic :)
-----Original Message----- From: Chris Hanson
Sent: Saturday, August 17, 2019 1:37 PM
To: Charles ; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Pinout for current loop interface
On Aug 17, 2019, at 9:14 AM, Charles via cctalk
<cctalk at classiccmp.org> wrote:
--
Nigel Johnson
MSc., MIEEE
VE3ID/G4AJQ/VA3MCU
Amateur Radio, the origin of the open-source concept!
You can reach me by voice on Skype: TILBURY2591
If time travel ever will be possible, it already is. Ask me again yesterday
This e-mail is not and cannot, by its nature, be confidential. En route from me to you, it
will pass across the public Internet, easily readable by any number of system
administrators along the way.
Nigel Johnson <nw.johnson at ieee.org>
Please consider the environment when deciding if you really need to print this message
I just hate having to make a custom cable for
every terminal and
computer I
own or work with ;)
Ah, but isn?t doing what so many before you have had to part of the
charm? :)
?-- Chris
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1:26 p.m.
On Sat, Aug 17, 2019 at 12:14 PM Charles via cctalk
<cctalk at classiccmp.org> wrote:
Given the problem you are trying to solve, if I were in your shoes,
since I have a lot of DEC gear, I would standardize on 8-pin
Mate-n-Lok connectors, but I have numerous devices already so equipped
(ASR33, VT52, VT220, VT100 w/20mA option, PDP-8 (various), DZ11
breakout panel...) Since I was just holding an original IBM PC serial
interface (as discussed above), I should probably bite the bullet and
make a DB25-8-pin-Mate-n-Lok cable for it, just in case (I happen to
have a couple of options for using ISA cards on Amigas, so it's even
multi-platform).
I happen to have a stash of the shells. What I should do is buy a bag
of the pins and get a reel of the 4-wire (R/G/B/W) cable that was
commonly used in the DEC world, then I'd be all set.
DB25s are easier to come by, but as has been mentioned, there's not
one way to wire them up and having a large stack of magic pin-swabber
cables is kind of a pain.
-ethan
I've never
heard of people using DB25 for 20mA, at least historically,
contemporaneous with
its widespread actual use. E.g. DEC universally used
'flat' 8-pin Mate-n-Lok connectors for 20mA serial connections.
Thanks for the comments... I asked mostly because the ADM-3A has both RS-232
and current loop interfaces built-in
1953
days inactive
1953
days old
5 comments
5 participants
participants (5)
-
billdegnan＠gmail.com -
charlesmorris800＠centurytel.net -
cmhanson＠eschatologist.net -
ethan.dicks＠gmail.com -
nw.johnson＠ieee.org